This relates generally to low energy BLE (Bluetooth Low Energy) networks, and more particularly to low power/low energy mechanisms and methods of establishing wireless connection between “nodes” of a scatternet or sensor network.
“Bluetooth” is a registered brand/trademark/certification mark for various wireless communication standards referred to herein as Bluetooth standards. The various Bluetooth standards have been developed and promulgated by the Bluetooth Special Interest Group known as “Bluetooth SIG”. The various brands/trademarks/certification marks are owned and licensed to various users by Bluetooth SIG., Inc. for use on and in conjunction with various communication devices. Up-to-date Bluetooth guidelines can be obtained from the Bluetooth SIG, Inc. website “https//www.bluetooth.org/en-us”. Proper authorized use of the Bluetooth brands/trademark/certification marks is enforced by Bluetooth SIG, Inc., in order to ensure that the standards are properly adhered to in accordance with the Bluetooth licensing terms and guidelines.
A Bluetooth Low Energy (BLE) brand/standard/certification mark is called “Bluetooth Smart”. The standard called “Bluetooth 4.0” incorporates the BLE or Bluetooth Smart standard. The term “classic Bluetooth” is used herein to refer to all versions of the Bluetooth standards prior to Bluetooth 4.0. All of the Bluetooth standards are developed by building certification standards/programs around certain parts of the IEEE 802.15.x family of specifications.
A “piconet” is basically a collection of slave/advertisers that are scanned by a master/scanner that could wirelessly connect to another piconet. A “scatternet” is a type of ad-hoc computer network consisting of two or more piconets. The terms “scatternet” and “piconet are typically applied to Bluetooth wireless technology. Bluetooth Low Energy (BLE) is a feature of Bluetooth 4.0 wireless radio technology aimed principally at low-power and low-latency applications for wireless devices with a short range, up to approximately 160 feet, and facilitates a wide range of applications.
FIG. 1 shows a conventional BLE scatternet including a piconet A and a piconet B each including a “master” or “master/scanner” device capable of wireless communication with a number of nearby “slave” or “slave/advertiser” devices. Bluetooth low energy (BLE) has the lowest power standard, and using BLE for the advertising of slave devices in a piconet provides the lowest known power consuming mechanism within the BLE standard. If it is desired to have the lowest power radio standard presently available, BLE is considered to be the starting point.
In piconet A, master/scanner 3-1 is capable of wireless communication with/advertisers 5-1, 5-2, 5-3, 5-4, and 5-5 through wireless links 2-1, 2-2, 2-3, 2-4, and 2-5, respectively. Similarly, in piconet B, master/scanner 10-2 is capable of wireless communication with/advertisers 5-6 and 5-7 through wireless links 2-6 and 2-7, respectively. Slave/advertiser 5-5 in piconet A also communicates with master 10-2 in piconet B through wireless link 7. In piconet A, master/scanner 3-1 can synchronize with any of the slave/advertisers in piconet A, for example as represented by reference numeral 15, to establish wireless link 2-1. After synchronization, master/scanner 3-1 then may perform two-way wireless data communication with the slave/advertiser, for example as represented by reference numeral 17. The BLE scatternet shown in FIG. 1 could include many more piconets that communicate with each other in essentially the manner described above. A shortcoming of the approach shown in FIG. 1 is that it fails to accommodate piconet slave/advertiser devices which must operate with very little power/energy because of the requirements of the BLE standards.
If achieving very low power consumption is not a concern, so-called ZigBee technology with its existing standard can be used. The BLE standard is part of the Bluetooth 4.0 standard and is interoperable with most mobile phones. ZigBee is a protocol that combines with the MAC (Media Access Control) protocol established by IEEE 802.15.4. It has multiple operational modes. It has been shown that advertisement is the lowest energy technique for wireless communication between “nodes” of scatternets. However, the ZigBee standard is not operable in mobile phones. As far as the BLE standard is concerned, there is a “single mode”, which is just the relatively new Bluetooth low energy mode of operation, and there also exists a “dual mode”, which supports “classic” Bluetooth standard operation as well as operation in accordance with the BLE low energy standard. Modern smart phones usually support both in order to be able to wirelessly connect in both modes with older smart phones and new very low energy Bluetooth phones and devices, respectively.
The Bluetooth standard specifies standard connection time intervals that are established at the beginning of the time interval during which slave/advertiser devices connected in a piconet are allowed to wirelessly communicate with other devices, but the communication connection intervals typically are limited to approximately four seconds. Because of drift in the synchronization of internal crystal-generated clock signals in the slave/advertiser devices in a piconet, is necessary for every slave/advertiser device in the piconet to “wake up” into a high power consumption condition approximately every four seconds. Such high power consumption is unacceptable in some applications. If all the slave/advertisers need to be very low energy devices, then slave/advertisers would not ordinarily be used to aggregate data generated by the slave/advertiser devices in a piconet during their allowed advertising time intervals and then wirelessly connect to the master/scanner of a different piconet, as shown by link 7 in the conventional system of FIG. 1.